The present invention relates to apparatus for reworking the valve guides of an internal combustion engine including apparatus for supporting and positioning a cylinder head during valve guide reworking operations.
The valve guides of an internal combustion engine become excessively worn during extended use. The tolerances between the valve stem and the valve guide must be maintained fairly close in order for the engine to operate efficiently. Heretofore, a fairly wide variety of tools, machines and supports have been proposed for use in repairing the valve guides of internal combustion engine cylinder heads. A typical method by which the valve guides are reworked includes the step of boring the worn valve guides, inserting a tubular insert and then reaming the insert to required tolerances. Such a method is taught, for example, in commonly owned U.S. Pat. No. 3,828,756 entitled Method and Apparatus for Rebuilding Valve Guides and issued on Aug. 13, 1974 to Kammeraad et al.
During the rebuilding and reworking of the valve guides, the cylinder head must be supported and positioned to permit the performance of the boring and reaming operations. Fairly large, complex and expensive machines have been developed for such reworking operations. These machines are large and relatively immovable and require the precise mounting of a cylinder head at a proper angle in order to produce the proper reworking alignment. Such machines typically include a heavy duty, geared head press, a custom table and an adjustable head cradle. The internal combustion engine cylinder head is mounted in the cradle which is adjustable to permit proper positioning of the head relative to the head press. Rotational and angular positioning of the cylinder head is necessary since many cylinder heads include canted or nonperpendicular valve guides.
Smaller tools mountable directly on the cylinder head and which permit the reworking of the valve guides with hand-operated tools have also been proposed. An example of one such apparatus may be found in commonly owned U.S. Pat. No. 3,764,204, entitled Valve Guide Boring Fixture and issued on Oct. 9, 1973 to Kammeraad. This patent discloses a generally U-shaped boring fixture mountable on a cylinder head at the valve guide. The fixture includes a guide arm securable to the cylinder head at the valve seat and a guide arm engageable with the cylinder head at the valve spring seat. The first guide arm includes an adjustably mounted axial bore adapted to guide various valve guide reworking tools. When using a valve guide boring fixture of this type, the cylinder head is supported on head support stands in order to provide sufficient clearance above and below the head to mount the boring fixture.
Different forms of cylinder head stands or holders have heretofore been proposed. Examples may be found in U.S. Pat. No. 3,261,599, entitled Cylinder Head Holder and issued on July 19, 1966 to Holmen and U.S. Pat. No. 3,048,387, entitled Holding Fixture for Cylinder Heads and issued on Aug. 7, 1962 to Waggoner. The cylinder head holder disclosed in the Holmen patent includes a base and a vertically extending tapered rod. The rod is adapted to be inserted through a bolt hole of a cylinder head. A pair of such holders are positioned at each end of the cylinder head to support the head in a single, nonadjustable position. The head may, however, be mounted on the holders with either side up.
The stand disclosed in the Waggoner patent includes a base plate and a cylindrical post through which extends a rotatable and transversely positionable rod. The rod supports on one end an elongated bar securable to the cylinder head and a segmental plate connected to the bar. The plate structure and rod permit the cylinder head to be rotated about an axis perpendicular to the top and bottom of the cylinder head and also swinging adjustment of the bar and head relative to the post. The stand disclosed in the Waggoner patent, therefore, permits some angular, rotational and vertical adjustment of the head relative to a bench or other support surface. Adjustment of the head is not, however, accomplished in a single vertical plane.
Heretofore, apparatus has not been available for adjustably supporting a cylinder head in a plurality of longitudinal and transverse axial positions within the same plane. Further, apparatus has not been available which would permit the reworking of the valve guides in a conventional drill press.